/*
 * Copyright (C) 2001-2012 Free Software Foundation, Inc.
 *
 * Author: Nikos Mavrogiannopoulos
 *
 * This file is part of GnuTLS.
 *
 * The GnuTLS is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 3 of
 * the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 *
 */

/* This file contains the code for the Max Record Size TLS extension.
 */

#include "gnutls_int.h"
#include "gnutls_errors.h"
#include "gnutls_num.h"
#include <gnutls_extensions.h>
#include <ext/max_record.h>

static int _gnutls_max_record_recv_params (gnutls_session_t session,
                                           const uint8_t * data,
                                           size_t data_size);
static int _gnutls_max_record_send_params (gnutls_session_t session,
  gnutls_buffer_st* extdata);

static int _gnutls_max_record_unpack (gnutls_buffer_st * ps,
                                      extension_priv_data_t * _priv);
static int _gnutls_max_record_pack (extension_priv_data_t _priv,
                                    gnutls_buffer_st * ps);

/* Maps record size to numbers according to the
 * extensions draft.
 */
static int _gnutls_mre_num2record (int num);
static int _gnutls_mre_record2num (uint16_t record_size);


extension_entry_st ext_mod_max_record_size = {
  .name = "MAX RECORD SIZE",
  .type = GNUTLS_EXTENSION_MAX_RECORD_SIZE,
  .parse_type = GNUTLS_EXT_TLS,

  .recv_func = _gnutls_max_record_recv_params,
  .send_func = _gnutls_max_record_send_params,
  .pack_func = _gnutls_max_record_pack,
  .unpack_func = _gnutls_max_record_unpack,
  .deinit_func = NULL
};

/* 
 * In case of a server: if a MAX_RECORD_SIZE extension type is received then it stores
 * into the session the new value. The server may use gnutls_get_max_record_size(),
 * in order to access it.
 *
 * In case of a client: If a different max record size (than the default) has
 * been specified then it sends the extension.
 *
 */

static int
_gnutls_max_record_recv_params (gnutls_session_t session,
                                const uint8_t * data, size_t _data_size)
{
  ssize_t new_size;
  ssize_t data_size = _data_size;
  extension_priv_data_t epriv;
  int ret;

  if (session->security_parameters.entity == GNUTLS_SERVER)
    {
      if (data_size > 0)
        {
          DECR_LEN (data_size, 1);

          new_size = _gnutls_mre_num2record (data[0]);

          if (new_size < 0)
            {
              gnutls_assert ();
              return new_size;
            }

          session->security_parameters.max_record_send_size = new_size;
          session->security_parameters.max_record_recv_size = new_size;
        }
    }
  else
    {                           /* CLIENT SIDE - we must check if the sent record size is the right one 
                                 */
      if (data_size > 0)
        {
          ret = _gnutls_ext_get_session_data (session,
                                              GNUTLS_EXTENSION_MAX_RECORD_SIZE,
                                              &epriv);
          if (ret < 0)
            {
              gnutls_assert ();
              return GNUTLS_E_INTERNAL_ERROR;
            }

          if (data_size != 1)
            {
              gnutls_assert ();
              return GNUTLS_E_UNEXPECTED_PACKET_LENGTH;
            }

          new_size = _gnutls_mre_num2record (data[0]);

          if (new_size < 0 || new_size != epriv.num)
            {
              gnutls_assert ();
              return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
            }
          else
            {
              session->security_parameters.max_record_recv_size = epriv.num;
            }

        }


    }

  return 0;
}

/* returns data_size or a negative number on failure
 */
static int
_gnutls_max_record_send_params (gnutls_session_t session, gnutls_buffer_st* extdata)
{
  uint8_t p;
  int ret;

  /* this function sends the client extension data (dnsname) */
  if (session->security_parameters.entity == GNUTLS_CLIENT)
    {
      extension_priv_data_t epriv;

      ret = _gnutls_ext_get_session_data (session,
                                          GNUTLS_EXTENSION_MAX_RECORD_SIZE,
                                          &epriv);
      if (ret < 0)              /* it is ok not to have it */
        {
          return 0;
        }

      if (epriv.num != DEFAULT_MAX_RECORD_SIZE)
        {
          p = (uint8_t) _gnutls_mre_record2num (epriv.num);
          ret = _gnutls_buffer_append_data( extdata, &p, 1);
          if (ret < 0)
            return gnutls_assert_val(ret);

          return 1;
        }

    }
  else
    {                           /* server side */

      if (session->security_parameters.max_record_recv_size !=
          DEFAULT_MAX_RECORD_SIZE)
        {
          p =
            (uint8_t)
            _gnutls_mre_record2num
            (session->security_parameters.max_record_recv_size);

          ret = _gnutls_buffer_append_data( extdata, &p, 1);
          if (ret < 0)
            return gnutls_assert_val(ret);

          return 1;
        }
    }

  return 0;
}


static int
_gnutls_max_record_pack (extension_priv_data_t epriv, gnutls_buffer_st * ps)
{
  int ret;

  BUFFER_APPEND_NUM (ps, epriv.num);

  return 0;

}

static int
_gnutls_max_record_unpack (gnutls_buffer_st * ps,
                           extension_priv_data_t * _priv)
{
  extension_priv_data_t epriv;
  int ret;

  BUFFER_POP_NUM (ps, epriv.num);

  *_priv = epriv;

  ret = 0;
error:
  return ret;
}


/* Maps numbers to record sizes according to the
 * extensions draft.
 */
static int
_gnutls_mre_num2record (int num)
{
  switch (num)
    {
    case 1:
      return 512;
    case 2:
      return 1024;
    case 3:
      return 2048;
    case 4:
      return 4096;
    default:
      return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
    }
}

/* Maps record size to numbers according to the
 * extensions draft.
 */
static int
_gnutls_mre_record2num (uint16_t record_size)
{
  switch (record_size)
    {
    case 512:
      return 1;
    case 1024:
      return 2;
    case 2048:
      return 3;
    case 4096:
      return 4;
    default:
      return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
    }

}

/**
 * gnutls_record_get_max_size:
 * @session: is a #gnutls_session_t structure.
 *
 * Get the record size.  The maximum record size is negotiated by the
 * client after the first handshake message.
 *
 * Returns: The maximum record packet size in this connection.
 **/
size_t
gnutls_record_get_max_size (gnutls_session_t session)
{
  /* Recv will hold the negotiated max record size
   * always.
   */
  return session->security_parameters.max_record_recv_size;
}


/**
 * gnutls_record_set_max_size:
 * @session: is a #gnutls_session_t structure.
 * @size: is the new size
 *
 * This function sets the maximum record packet size in this
 * connection.  This property can only be set to clients.  The server
 * may choose not to accept the requested size.
 *
 * Acceptable values are 512(=2^9), 1024(=2^10), 2048(=2^11) and
 * 4096(=2^12).  The requested record size does get in effect
 * immediately only while sending data. The receive part will take
 * effect after a successful handshake.
 *
 * This function uses a TLS extension called 'max record size'.  Not
 * all TLS implementations use or even understand this extension.
 *
 * Returns: On success, %GNUTLS_E_SUCCESS (0) is returned,
 *   otherwise a negative error code is returned.
 **/
ssize_t
gnutls_record_set_max_size (gnutls_session_t session, size_t size)
{
  ssize_t new_size;
  extension_priv_data_t epriv;

  if (session->security_parameters.entity == GNUTLS_SERVER)
    return GNUTLS_E_INVALID_REQUEST;

  new_size = _gnutls_mre_record2num (size);

  if (new_size < 0)
    {
      gnutls_assert ();
      return new_size;
    }

  session->security_parameters.max_record_send_size = size;
  epriv.num = size;

  _gnutls_ext_set_session_data (session, GNUTLS_EXTENSION_MAX_RECORD_SIZE,
                                epriv);

  return 0;
}
